Scanning Electron Microscopic Observations of the Mesenchyme Cells in the Larvae of the Starfish Pisaster ochraceus

The are two morphological types of mesenchyme cells, bipolar and multipolar, and both are derived from the tip of the archenteron at the gastrula stage. Some of the cells form larval muscle and others may be involved in the stomodeum and coelomic pouch formation.     

Yeast tRNA Leu UAG. Purification, properties and determination of the nucleotide sequence by radioactive derivative methods.

A second major species of leucine tRNA, tRNA Leu UAG (formerly designated tRNA Leu CUA) was purified from baker's yeast in a three-step procedure entailing BD-cellulose chromatography in the presence and absence of Mg2+ and Sephadex G-100 gel filtration. Results of aminoacylation and partial RNase T1 digestion experiments showed that this tRNA retains a native conformation under conditions that denature yeast tRNA Leu m5CAA (tRNA3 Leu). The primary structure of baker's yeast tRNA Leu UAG was elucidated by application of sensitive radioactive isotope derivative ("postlabeling") methods. Complete RNase T1 and A and partial RNase U2 fragments, prepared from non-radioactive tRNA and 5'-half and 3'-half molecules, were separated by two-dimensional polyethyleneimine-cellulose anion-exchange thin-layer chromatography and isolated by a novel micropreparative procedure affording high yields of these compounds in sufficient purity for subsequent tritium derivative analysis. Base composition and sequence of oligonucleotides were analyzed by tritium derivative methods. Molar ratios of the fragments were determined from the radioactivity of 3H-labeled nucleoside trialcohols in combination with base analysis. 2'-O-Methylated guanosine was characterized using the [gamma-32P]ATP/polynucleotide kinase reaction. The analysis of classical complete and partial RNase digests by the tritium derivative methods yielded the complete nucleotide sequence of the tRNA. A total of about 20 A260 units of the RNA was used for analysis, i.e. considerably less material than required for conventional spectrophotometric analysis. A different sequencing approach, consisting of a combination of "readout sequencing" with tritium sequencing of complete RNase T1 and A fragments, was applied to the 3'-half molecule. The 3'-half molecule was labeled with 32P at its 5' terminus, partially degraded with RNase T1, U2, and Phy1 and with alkali, and subjected to polyacrylamide gel electrophoresis. The sequence was read off the gel on the basis of cleavage patterns and size of the fragments. While the readout procedure provided only the positions of A, U, C, and G residues in the chain, additional information from tritium derivative analysis was utilized to define the positions of the modified nucleosides. The readout sequencing procedure was found to require less than 0.01 A260 unit of RNA and the analysis of the complete fragments about 6 A260 units. Interesting structural features of tRNA Leu UAG are (a) the location of unique, leucine tRNA iso-acceptor-specific sequences next to U-8, a constant nucleotide participating in synthetase recognition, (b) the occurrence of 1-methyladenosine in the T loop, a modification not present in the structurally related tRNA Leu m5CAA, and (c) the unusual presence of an unmodified uridine in the first position of the anticodon, which may be related to the unusual coding properties reported for this tRNA.     

Probabilistic Assessment of Industrial Synergistic Systems

A probability‐based method is presented for assessing the reliability of synergistic systems and their ability to cope with the uncertainties often associated with two of a company's main types of activities: those carried out by the manufacturing department, and those carried out by the storage department. This method is based on a model focusing on the dynamic simulation of synergistic flows in terms of the mass balance. It differs from previous material flow analysis tools, which do not take into account the temporary failures occurring at the companies involved and the resulting loss of production capacity. The failure events occurring at any of the companies in a synergistic system may result in various levels of synergy failure and a short supply of resources for other companies. We therefore propose to identify the main factors responsible for a lack of synergy. We developed a dynamic stock simulation model for assessing the reliability of synergistic systems as well as that of the individual companies of a system before and after a synergy is set up. We first confirm the validity of this model by comparing the results with those based on the binomial theorem in system reliability analysis, and we then apply the model to the case of an industrial system. We conclude that companies involved in a synergistic system will inevitably be exposed to a higher risk of resource shortage because of the unsteady synergistic and outsourcing flows on which they depend. More efficient stock management methods would prevent the occurrence of the risks often associated with synergistic flows.     

秦岭川金丝猴一周岁内个体的行为发育

2003年3月至2004年5月在陕西周至国家自然保护区的玉皇庙地区,采用目标动物取样法(Focal ani-mal sampling)对2003年出生的5只金丝猴个体行为发育进行了观察,应用全事件记录法(All-occurrences record-ing)进行数据的收集。结果表明23日龄婴儿首次从母亲怀内爬出在树枝上活动,68日龄开始在树上攀爬跳跃,5月龄主动采食树叶和啃投食区食物,6月龄跟随社群迁移。依据婴幼儿主要行为首次出现时间及其变化,把1周岁内个体发育分为5个时期,即完全依赖期、探索外部世界期、融入社群期、适应生存期和逐步独立期。1周岁内婴幼儿活动和休息的地方是母亲怀里、其它个体怀里、树枝上和地面上。随着发育,婴幼儿在这些地方停留的时间也在变化。1周岁内婴幼儿在母亲怀中的时间与年龄存在明显的负相关,在其它个体怀里的时间与年龄也呈显著负相关。虽然独自在树上的时间与年龄相关性不显著,但在地面上停留的时间与年龄呈正相关。     

Drosophila rolling pebbles: a multidomain protein required for myoblast fusion that recruits D-Titin in response to the myoblast attractant Dumbfounded.

The fusion of myoblasts leading to the formation of myotubes is an integral part of skeletal myogenesis in many organisms. In Drosophila, specialized founder myoblasts initiate fusion through expression of the receptor-like attractant Dumbfounded (Duf), which brings them into close contact with other myoblasts. Here, we identify Rols7, a gene expressed in founders, as an essential component for fusion during myotube formation. During fusion, Rols7 localizes in a Duf-dependent manner at membrane sites that contact other myoblasts. These sites are also enriched with D-Titin, which functions to maintain myotube structure and morphology. When Rols7 is absent or its localization is perturbed, the enrichment of D-Titin fails to occur. Rols7 integrates the initial event of myoblast attraction with the downstream event of myotube structural organization by linking Duf to D-Titin.     

Weaning Age,Infant Care,and Behavioral Development in <Emphasis Type="Italic">Trachypithecus leucocephalus</Emphasis>

Primate infants are born in an altricial state and rely on the care of their parents for a relatively long period of time. Parental investment is critical to offspring survival and thus to the reproductive success of the parent as well. However, mothers and infants may experience a conflict of interest, in that infants may benefit by receiving prolonged maternal care but mothers may curtail such care in a tradeoff between investment in current versus future offspring. Documenting life history characteristics, such as age at weaning, is important not only for understanding the conflicts of interest and tradeoffs; such information can also provide insights about female reproductive rates and be valuable for conservation efforts. Little is known about the life history of white-headed langurs (Trachypithecus leucocephalus), despite their endangered status. We were the first to investigate mother-infant relationships and infant behavioral development in the species. We studied 3 wild mother-infant pairs throughout infancy. We used data from >460 h of focal subject sampling to calculate the proportion of time individuals spent in different behavioral states and the frequency of instantaneous events, such as maternal rejection. White-headed langur infants depended on their mothers for 19–21 mo, at which time they were weaned. Maternal rejection facilitated infant independence in the early stages of infant development, and mothers stopped investing in their infants when they resumed estrus. The weaning age of the wild white-headed langurs we studied was dramatically longer than that of captives, possibly as a result of the nutritional differences between wild and captive populations. Weaning age was also longer than for most other Asian colobines, and may be attributable to the degradation and fragmentation of their natural habitat.     

Natriuretic peptides stimulate the cardiac sodium pump via NPR-C-coupled NOS activation

Natriuretic peptides (NPs) and their receptors (NPRs) are expressed in the heart, but their effects on myocyte function are poorly understood. Because NPRs are coupled to synthesis of cGMP, an activator of the sarcolemmal Na(+)-K(+) pump, we examined whether atrial natriuretic peptide (ANP) regulates the pump. We voltage clamped rabbit ventricular myocytes and identified electrogenic Na(+)-K(+) pump current (arising from the 3:2 Na(+):K(+) exchange and normalized for membrane capacitance) as the shift in membrane current induced by 100 micromol/l ouabain. Ten nanomoles per liter ANP stimulated the Na(+)-K(+) pump when the intracellular compartment was perfused with pipette solutions containing 10 mmol/l Na(+) but had no effect when the pump was at near maximal activation with 80 mmol/l Na(+) in the pipette solution. Stimulation was abolished by inhibition of cGMP-activated protein kinase with KT-5823, nitric oxide (NO)-activated guanylyl cyclase with 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ), or NO synthase with N(G)-nitro-L-arginine methyl ester (L-NAME). Since synthesis of cGMP by NPR-A and NPR-B is not NO dependent or ODQ sensitive, we exposed myocytes to AP-811, a highly selective ligand for the NPR-C "clearance" receptor. It abolished ANP-induced pump stimulation. Conversely, the selective NPR-C agonist ANP(4-23) reproduced stimulation. The stimulation was blocked by l-NAME. To examine NO production in response to ANP(4-23), we loaded myocytes with the NO-sensitive fluorescent dye diacetylated diaminofluorescein-2 and examined them by confocal microscopy. ANP(4-23) induced a significant increase in fluorescence, which was abolished by L-NAME. We conclude that NPs stimulate the Na(+)-K(+) pump via an NPR-C and NO-dependent pathway.     

Innovative use of Thiobacillus ferrooxidans for the biological machining of metals

Preliminary results on the novel use of the bacterium Thiobacillus ferrooxidans (ATCCJ 3598 and ATCC33020) for the micro‐machining (or biomachinig) of metals are reported. Biomachning is a controlled microbiological process to selectively form microstrucutures on a metal work‐piece by metal removal (or dissolution) using microorganisms. Applying copper and mild steel as work‐pieces, it was shown that the mass removed increased proportionately with machining time. In another experiment, the work‐pieces were coated with organic photo‐resistive materials to mask (i.e. protect) certain regions of the metlas, thereby defining the microstructure to be formed. The unmasked regions were successfully biomachined; the final machined profile was shown to be similar to the coating image on the original metal. Although biomachining proceeded at a slower rate than chemical machining, the undesired leaching of the metal in the region under the masked area (termed undercutting) was not as severely encountered when compared with the latter. This work demonstrates the potential use of microorganisms for the biomachining of metals. As a “green process”, the innovative use of T. ferrooxidans for the micro‐machining of metals opens up the possibility of biomachining as an alternative to conventional metal processing.     

Maculatin 1.1, an anti-microbial peptide from the Australian tree frog, Litoria genimaculata solution structure and biological activity.

The dorsal glands of Australian tree frogs from the Litoria species contain a diversity of antibiotic peptides that forms part of the defence system of the animal. Here, the antibiotic activity and structure of maculatin 1.1, a 21 amino acid peptide from Litoria genimaculata, are compared. The activity data on maculatin 1.1 and a series of its analogues imply that the mechanism of action of maculatin 1.1 involves binding to, and subsequent lysis of, the bacterial cell membrane. The structure of maculatin 1.1 was determined using NMR spectroscopy in a trifluoroethanol/water mixture and when incorporated into dodecylphosphocholine micelles. Under both conditions, the peptide adopts a very similar conformation, i.e. a helical structure with a central kink in the vicinity of Pro15. The kink allows the peptide to adopt a well-defined amphipathic conformation along its entire length. The similar structures determined under both solvent conditions imply that structures of membrane-interacting peptides in trifluoroethanol/water mixtures are representative of those adopted in a membrane environment, e.g. when incorporated into micelles. The synthetic Ala15 analogue of maculatin 1.1 has markedly reduced activity and its NMR-derived structure is a well-defined helix, which lacks the central kink and flexibility of the parent molecule. It is concluded that the kink is important for full biological activity of the peptide, probably because it allows maximum amphipathicity of the peptide to facilitate interaction with the membrane. The structure of maculatin 1.1 is compared with a related peptide, caerin 1.1 [Wong, H., Bowie, J.H. and Carver, J.A. (1997) Eur. J. Biochem. 247, 545-557], which has an additional central proline residue and enhanced central flexibility compared with maculatin 1.1. The role of central flexibility within antibiotic peptides in their interaction with bacterial membranes is discussed.